Process of preparing keto acids



PROCESS OF PREPARING KETO ACIDS Muus G. I. Beets and Wilhelmina Meerburg, Hilversum, Netherlands, assignors to N. V. Polak & Schwarzs Essencefabrieken, Hilversum, Netherlands No Drawing. Application June 6, 1955 Serial No. 513,444

Claims priority, application Netherlands July 2, 1954 13 Claims. (Cl. 260-413) The present invention relates to a process for the preparation of delta keto acids.

Delta keto acids of the type in which R is a substituted or non-substituted aliphatic hydrocarbon radical, can be considered as valuable raw materials for the preparation of a great number of prodnets of divergent structure, many of which are of economic importance.

Thus, by reducing these keto acids, lactones which are applied as odoriferous substances can be prepared in the following manner:

RCH(CH:)3COOH RCH(CH2):C=O

(1 They can also be converted into fatty acids of varied structure by total reduction of the keto group:

R-fiKCHQsCOOH R(CH2)4COOH (III) This process can also be applied for the preparation of valuable macrocyclic lactones by selecting group R so that it contains a reactive group which is preferably terminal, e. g. a double bond, a hydroxyl group, an acyloxy group or a halogen atom which is able to react directly or indirectly with the carboxyl group, as follows:

HO(CH2)m-ACOOH (CH2)m-HO 0 The purpose of the present invention is to provide a method of preparing delta keto acids of type (I) in a simple manner from readily avialable raw materials.

For this purpose, we start from compounds of the following type:

CHaC

B omii-oh fit ice

in the following manner:

0 (VII) In general, compounds of type V cannot be distilled but they can be converted into the desired keto acids in crude form according to the present invention, by which the simplicity of the process is still further increased.

The preparation of compounds of the type (V1) is very simple since the cyan ethylation method and its variants may be used, i. e. the condensation of an ester of acetyl acetic acid with acrylonitrile, acrylamide or esters of acrylic acid under the influence of alkaline catalysts. This is illustrated by the following reaction schemes where in Et represents ethyl and Me methyl:

(VIII) 011300 CHQC o OEt CHFCHC CH1CH:C

CHaCOC COOEt oruooofliooout CHFCHCOOM6 cmomoooMe CHaCOC coont (x) The present invention is based on a selective splitting otf of the smallest acyl group from compound V, whilst maintaining the largest acyl group, by alkaline hydrolysis or by alcoholysis, followed by or preferably simultaneously with saponification of group A to a carboxyl group and removal of group B, by hydrolysis and decarboxylation.

It is very surprising that this result can be obtained in one single operation by treating compound V either in crude or in purified form, diluted with a solvent or not, with aqueous lye to which alcohols or other substances may be added or not.

Furthermore it also is surprising that the reaction conditions, especially the temperature, the kind and concentration of the lye and the kind of the solvent, if any, added, may be varied substantially in an unlimited way without this having any influence of importance on the yield. It is not important either whether the lye is added to the ester to be hydrolysed or that one proceeds in the reversed manner.

Treatment preferably is carried out with soda or potash lye of 10-25% as the hydrolysing agent, whilst it seems that the yield is somewhat favorably influenced by having the reaction proceed quickly. For this purpose one preferably operates at 70-100 C.

Although this means a superfluous complication for the preparation of the delta keto acids in general, as already indicated above, if desired the reaction may take place in two separate stages. In this case the ester V is first treated in an alcohol and in the presence of a catalytic quantity of a catalyst suitable for this purpose, e. g. an alkali metal alcoholate, an alkali metal hydroxide or ammonia. In this treatment also, the reaction conditions can be varied within wide limits. E. g. the mixture may be allowed to stand during some hours at room tem- Patented Jan. 21, 1958 perature=or-it-=may beheated to the boiling point for 44 /2. hour.

During this treatment, the smaller of the two acyl groups is primarily split off; according to the following scheme in which R"OH represents-the-alcoh'ol in-which the alcoholysis is carried out:

Aftenpurificatiorrornot the product obtained can then b .converted;into the desired. keto acid I by hydrolysis with aqueous. lkal -J q wpr t ge process,however, does not give an improyementofiy cld incomparisonwith. the one-stage operationlslgell wojcikzand Adkins. (1.; Am. Chem. Soc. 54 (.1232) 7. -).1ha. devotedan extensive examination to hr..'.que .ti 2 ;whether.it gis .possibleto prepare keto acids I from esters of type ;V.;; The-methodsexamined by these apthors are: alcoholysis at 60 C. under influence of hydrochloricaeid and alcoholysis at 150-250" C. and 100 atmospheres L i In allgexperiments (with the exception of one single case in which R was an aromatic group) it appeared, however, that mainly thedargest of the two acyl groups was split off.

Therefore it is surprising that in contradistinction with the results of Isbell et -al. it appeared to be possible to splitpif mainly the smallest of the two acyl groups from V andtoprepare the desired keto acid in good yield.

The invention is eluci dated by the following examples.

, EXAMPLE 1 Preparation of..4;ket o tetradegene-lj carboxylicgacid-l Qne. brings. .66.8 g. (2.75 mol) of magnesium and 725 g. of absolute .benzeneinto a reaction apparatus. One adds 15 g. of carbon tetrachloride, heats to boiling and adds 15 gfof absolute ethanol in 10 minutes. When the reactionsta-rts one adds gradually 238 g. of absolute ethan01 and.thereupqn,..also.under boiling, slowly 594 g. 2.75 mol) 'of methyl 4-ketg3-etoxy carbonylpentane carboxylate. Onethereuponboils foranothen 1 /2 hour, cools to 25. Cgand adds-.506 g. -(2.5 mol) of decene-9 carboxylic acid chloride: .dropby. .drop during hour.-

. Stirringais.continuedsduring.Mi hour at 25 C. and thereupon fonsome time at135 C. and then undercooling in.1ice -Water- 1500 :'g.of.- l%- sulphuric acid are added.

After..-Working..up -and.tdistilling..-oif tliebenzene 989 g.

of crude methyl 4-keto 3-acetyl 3-ethoxycarbonyl-tetrade.cene.-13.= carboxylate arenobtained. 395.5 g. of this crude; product are heated to boiling with 1000 got metha- 1 1aand in25 minutes 600g. ofsoda lye 31% are added.

Boiling is continuetlfor .25 minutes and the methanol is distilled off. Oneawor-ks up .with benzene .and recrystallizes theketo tetradecene carboxylie acid from petroleumether. .Th6.,-yild.lS{;48% oftheJtheory; calculated on'the acid chloride used. Melting point 68-685"? After reduction. ofrthecketo .group. this componnd can according to the .Netherlands Patent No. 67,45 8 be converted into the valuablepdoriferonssubstance penta-.

Preparation of 4-ket jetradecene-13 carboxylio acid-1 EfimPkL- djQi ofj et o y. alcu a don he iqshloride-a Matn poiater-asa c...

EXAMPLEB Preparation of 4-keto tetradecene-13' carboxylic acid-1 One prepares crude methyl keto acetyl ethoxy-carbonyl tetradecene carboxylate according to Example 1. One heats a mixture of 800 g. bf-fsodilye 12.5% and adds 196 g. of crndecondensation product with. stirringin M hour. One continues stirring until the reaction is complete'and works up.v Yield 50% =of;theitheorya calculated omthe acid. chloridepusedz. Melting point-6768:? Cs 7 EXAMPLE' Preparation of 4 keto,tetradeeenefl3, carb'oxylic acid-1' EXAMPLE. 5

Preparation of ;4-keto tetradecenerl 3 a carboxylic acid-1 One condenses methyl 'keto *ethoxycarbonyl' pentane carboxylate with decene carboxylicacid. chloride. accord ing to Example 1;

After completion of the condensation reaction one adds.

a solution of 5.8 g. (0.25 mol) of sodium in 402' g. of

absolute ethanol and then boils during /z houru One cools to room temperature and acidifies with 10% sulphuric a cidu After 'washingone'distills off the benzene completelyend adds 2000 g. of methanol. One heats to-boiling andadds 1200 g. of 33% soda lye drop by drop:

After completio'n-of'the hydrolysis one works up acv cording to. Example ..1.; Theketo.,tetraadecene carboxylic acid is obtained in a yield of 49% of the;.theory, calculated on the acid chloride brought to reaction. Melting point 67-68". 'C.'.

EXAMPLEFG 5 Preparation of4-ket.o.:decane. :carboxylic acid-1 1426 g. (6.6rnol') of rnethyl"4-keto Fethoxycarbonyl pentane carboxylate are condensedw-ithr89l .g. (611101) of hexane carboxylic acid chloride with the aid of 160.4 g. -of :magnesium--(6.6 mol), according to Example 1. After. removal. of the solvent 1849 g. of crude methyl 4-keto 3-acetyl 3-ethoxycarbonyl .decane carboxylate-l are obtained. 80,0 of; 12.5%.::soda -lye;;are-.-heated;to C. and 154 1g. of;thegcrndeicondensation:product are added drop 1 by drop. :in;;%'-;.hour. ;with;.stirr.ing.; Heating is continued until thQ'hYClBOIYSiS .is completes: One pours out into 650 g. of 20% sulphuric acid and;works ;up; The crude keto acid is distilled in 'vacuo and recrystal lized from petroleum, ether. The eyield amounts to 46% of the theory, calculated on the hexane carboxylic acid chloride brought to reaction. Melting point 57. 5-58.5 C. 36.3% of the theory of hexanecarboxylic acid are obtained as a by-product.

EXAMPLE?" Preparation of: -4- ket0 :de'cane 'carboxy lio acid-1* To 2000 g. of 5% soda lye which has been..-heated;to C; 1 ds: 15 dge-of 'crude; methylgketozracetyl ethoxycarbonyl; decane ecarboxylatee prepared according a'szasot EXAMPLE 8 Preparation of 4-keto decane carboxylic acid-1 One heats 300 g. of soda lye 33% to 70 C. and adds 154 g. of crude methyl keto acetyl ethoxycarbonyl decane carboxylate prepared according to Example 6 in 20 minutes with stirring. One heats until the reaction is complete and works up. The yield amounts to 40% of the theory. Melting point 57.558.5 C.

EXAMPLE 9 Preparation of 4-ket0 decane carboxylic acid-1 One heats 800 g. or" potash lye to 70 C. with stirring. One adds 154 g. of crude methyl keto acetyl ethoxycarbonyl decane carboxylate in 15 minutes with stirring which is continued until the reaction is complete. Duration approximately 1 hour. One pours out into dilute sulphuric acid and works up. The yield amounts to 45% of the theory. Melting point 58.5-59.5 C. One recovers hexane carboxylic acid as a by-product.

EXAMPLE 10 Preparation of 4-ket0 decane carboxylic acid-1 One heats to boiling 800 g. of 12.5% of soda lye and adds 154 g. of crude methyl keto acetyl ethoxycarbonyl decane carboxylate, prepared according to Example 6 in A hour. One boils during 1 hour and works up. The yield amounts to 46% of the theory. Melting point 57.5-58.5 C. One obtains as a by-product 23 g. of hexane carboxylic acid.

EXAMPLE 11 Preparation of 4-ket0 decane carboxylic acid-1 One heats to boiling a mixture of 300 g. of soda lye 33%, 200 g. of water and 300 g. of alcohol and adds 154 g. of crude methyl keto acetyl ethoxycarbonyl decane carboxylate in 20 minutes. One continues stirring until completion of the reaction, distills off the alcohol and works up in the usual way. The yield amounts to 48% of the theory, whilst 22.5 g. of hexane carboxylic acid are recovered.

EXAMPLE 12 Preparation of 4-keto decane carboxylic acid-l One heats to boiling 200 g. of 5% soda lye and adds 154 g. of crude methyl keto acetyl ethoxycarbonyl decane carboxylate, prepared according to Example 6, in 14 hour. One boils until the reaction is complete and works up. The yield amounts to 48% of the theory. Melting point 58.559.5 C.

EXAMPLE 13 Preparation of 4-keto decane carboxylic acid-1 One heats 500 g. of 20% soda-lye to 40 C. and at this temperature one adds 154 g. of crude methyl keto acetyl ethoxycarbonyl decane carboxylate, prepared according to Example 6, in 10 minutes. One continues stirring until saponification is complete and Works up, in the usual way. The yield of keto decane carboxylic acid amounts to 43% of the theory calculated on the acid chloride. Melting point 58.559.5 C.

EXAMPLE 14 Preparation of 4-ket0 decane carboxylic acid-1 One condenses 594 g. of methyl 4-keto 3-ethoxycarbonyl pentane carboxylate with 371 g. of hexane carboxylic acid chloride with the aid of 66.8 g. of magnesium, according to Example 1.

When the condensation is complete one adds a solution of 5.8 g. of sodium in 402 g. of absolute ethanol and boils during /2 hour. One acidifies, washes to neutral reaction and removes the solvent. When distilling, 34% of the theory of ethyl hexane carboxylate, 39% of the theory of ethyl 4-keto 3-ethoxycarbonyl pentane carboxylate, and

. EXAMPLE 15 Preparation of 4-keto nanane carboxylic acid-1 According to Example 1 one condenses 197 g. of 3- ethoxycarbonyl 4-keto pentane carboxylic acid nitrile with 132 g. of capronic acid chloride with the aid of 26.2 g. of magnesium. After completion of the condensation reaction the crude reaction product is worked up according to Example 13 in one operation or according to Example 14 in two operations. One continues the hydrolysis until no ammonia escapes anymore. In both cases keto nonane carboxylic acid is obtained in a substantially equal yield. Melting point 5555.5 C.

EXAMPLE 16 Preparation of 4-ket0 undecane carboxylic acid-1 According to Example 1 one condenses 594 g. of methyl 4-keto 3-ethoxycarbonyl pentane carboxylate with 406 g. of heptane carboxylic acid chloride with the aid of 66.8 g. of magnesium.

After completion of the reaction one adds a solution of 10 g. of potassium in 402 g. of ethanol. One boils during /2 hour, cools and adds 2000 g. of sulphuric acid 10% with cooling and stirring. One washes to neutral reaction, distills oii the solvent and fractionates the residue.

One obtains 32% of the theory of recovered heptane carboxylic acid, 32% of the theory of ethyl 4-keto 3- ethoxycarbonyl pentane carboxylate and 56% of the theory of ethyl 4-keto 3-ethoxycarbonyl undecane carboxylate (439 g.).

Mixed with 878 g. of methanol the latter is heated to boiling and 509 g. of 33% soda lye are added drop by drop. After completion of the hydrolysis methanol is distilled ofi and the reaction product is acidified with dilute sulphuric acid.

After working up and recrystallisation the keto acid is obtained in a yield of 46% of the theory calculated on the heptane carboxylic acid chloride brought to reaction. Melting point 6768 C.

If the reaction is carried out in one operation by saponifying the crude condensation product with boiling 15% soda lye the same yield is obtained.

. EXAMPLE 17 Preparation of 3-ket0 nonane carboxylic acid-1 According to Example 1 one condenses 594 g. of ethyl 3-keto 2-ethoxycarbonyl butane carboxylate with 371 g. of hexane carboxylic acid chloride with the aid of 66.8 g. of magnesium.

One obtains 842 g. of crude ethyl 3-keto Z-acetyl 2-ethoxycarbonyl nonane carboxylate-1.

In 15 minutes one adds 168 g. of this crude reaction product to 800 g. of 12.5% soda lye which have been heated to boiling. One boils for a further hour, acidifies with 1300 g. of 10% sulphuric acid and purifies the crude acid by vacuum distillation and by recrystallisation from petroleum ether. The yield amounts to 55% of the theory calculated on the hexane carboxylic acid chloride brought to reaction. Melting point 68-685 C.

EXAMPLE 18 Preparation of 14-hya'r0xy 4-keto tetradecane carboxylic acid-1 According to Example 1 one condenses 706.5 g. (2.5

reactiomonezadds. 1500-;cn1k of. sulphuric acid. 1 and after; washing; one distills; off; the solvent. Theweight; of-

the .crude;et hylc 4.-keto--3-acetyl;3-ethoxycarbonyl 14-bromo.

tetra'decane; carboxylateyamounts to 1227; g;

48.00ag',- .of 12.5%; soda.lye.'( 15;rn0l). are.-heated.to,. boil.

ing, and one adds-z 1227 g-,. of. crude:;condensatiorr productj drop by drop in minutes with boiling and stirring.

One boils during 4 hours, cools. to room temperature and adds 1700 g. of sulphuric acid while cooling. One adds 125.0xcnn3ofchenzeneyone heats'-to.70C..while stirring and adds 100g. of acetic acid. Oneseparates off the benzenic layer-,7 washesrwithwarmwater. andlcools to.

10 CL. A' mixture of{ l4'-hydroxy 4-keto. tetradecane carb'oxyli' c acid and' .l'O-hyd'roxy. decane carboxylic, acid. crystallizes, out One filters, and. dries... Weight .435 g, When. separatir'ig one, obtains. 14hydroxy 4-ketoste tra1' decane carboxylicacidf with'melting point 88.-89 C. in.

a yield] of %i calculatedonthe bronio'decanecarboxylic.

acid chloride, brought to reaction.

After reduction of'the keto group thiscompound-can.

be converted into the valuable odoriferous substance pentadecanolide by cyclizatiom What weclaim; is:

l. A process for the preparation of delta keto acids of th e general formula R;O(CH OOH, comprising subjecting toalkaline solvolysis including alkaline hydrolysis adiaeyl derivative of the general formula RCO (GHQ-2A wherein Aiandj B are. groups which may be hydroliz'ed' tocarboxyl groups, and Ris-selected from the groupcon- SiStingpfQSuI'istimted' and nomsubstituted aliphatic hydro:

carbon groups.

2. Theprocess, of claim. 1,,wherein-thehydrolysis is.

effected in the presence of a solvent.

3. The.process,of claim. 1, wherein the diacyl: derivative is. subjected to.v alkaline. .alcoholysis followed. by hyd'rolysis.vv

v 4. Theprocess of. claim 3., wherein thealcoholysis is. effected in the presence of an alkaline=reacting catalyst:

5.;Theprocessof; claim.1,.wherein the diacyl derivative is subjected toalkalinemlcoholysis in the presenceof an allialinerreacting'.catalyst; thereaction product. is at least, partially purifiedand the at least partiallypurified. reactionproduct is .subjected .to hydrolysis.

6;. Themrocessoi claim 1,, whereimthe diacyl deriyag tive is subjected to alkaline. hydrolysis with a. l0 2'5'%" aqueous solution of an alkali hydroxide.

7. The process of cl'air'rr- 1; wherein the hydrolysis is carried;out;aha-temperature:between:about. C. and theboiling temperature of the reaction medium.

wherein A and B are groups-selected. from the group consisting of ester, amide andcyau groups, and R is selected from the group concisting of substituted and nonsubstituted aliphatic hydrocarbon groups.

9. The.processof claim 8., wherein the hydrocarbon groups arealkyl groups.

10; A process: for the preparation of hydroxy deltalteto acids,-,comprising-, subjecting to. alkaline solvolysis including alkaline; hydrolysis a diacyl. derivative of the;

general formula. I

' Boo ennui O CHsCO B wherein A and B are groups which may be hydrolyzed to carboxyl groups, R is a substituted aliphatic hydrocarbon containing-a reactive group which maybe hydrolyzed to a hydroxylgroup. 7 l l. Theprocess'of claim 10 for the preparation of 1" hydroxy-4-keto-tetradecane carboxylic acidl, wherein: the largest acyl group in the diacyl derivative is X being; athalogenatom.

12. A process for the preparation ofunsaturated deltaketo acids', comprising subjecting'to alkaline solvolysis including'alkaline hydrolysis a diacyl'derivative of the genera-l formulav RCO V (CH2)2A CHQ'CO B wherein A and B'aregroups which may be hydrolyzed to carboxyl groups, and R is selected from the 'group consisting of substitutedxand non-substituted.aliphatic hydrocarbon groupscontaining a double bond.

' 13. The. process of claim. 12 for the preparation of;4-'

keto tetradecene-13-carboxylic acid-l; wherein the largest acyl group in the diacyl derivative is References Cited. in the .file of this patent Isbell-etaL: I. Am. Chem. Soc., vol. 54, page .3678 I Adams: et; al.:

OrganicReactions;fv0ll 1, page" 301 (Copyright 1942). a 

8. A PROCESS FOR THE PREPARATION OF DELTA KETO ACIDS OF THE GENERAL FORMULA R,CO(CH2)3COOH, COMPRISING SUBJECTING TO ALKALINE SOLVOLYSIS INCLUDING ALKALINE HYDROLYSIS A DIACYL DERIVATIVE OF THE GENERAL FORMULA 